1. Field of the Invention
The present invention relates to a vibration apparatus capable of generating and externally transmitting a sound wave of audible frequency and transmitting a vibration for notification, which is provided in a communication device such as a portable phone, a beeper or the like to selectively perform a sounding function and a vibrating function relying upon a frequency of a current inputted therein.
2. Description of the Related Art
Generally, the notification of the reception of an incoming call in a portable communication device can be performed by a sounding function and a vibrating function. Between these two functions, the sounding function by which bell or speaker sound can be discharged is mainly used, and the sounding function can be converted into the vibrating function to be used in such a situation where a silent atmosphere must be inevitably maintained.
In order to perform the sounding function and the vibrating function, a micro-speaker and a vibrating motor are provided in a communication device to be selectively operated in compliance with an instruction inputted by a user.
Referring to FIG. 1, there is shown a longitudinal cross-sectional view illustrating a construction of a conventional micro-speaker. The micro-speaker includes a case 1. A magnet 2, a voice coil 3 and a vibrating coil 4 are arranged in the case 1. In other words, the magnet 2 is secured at a center portion in the case 1. A cylindrically formed voice coil 3 is arranged around the magnet 2 such that it surrounds the magnet 2, and an upper end of the voice coil 3 which extends upward through the case 1 is attached to a vibrating coil 4. The magnet 2 has N and S poles which are stacked one up the other, and a portion adjacent to an edge of the vibrating coil 4 to which the voice coil 3 is attached, is securely fastened to a fastening member.
Accordingly, if a high frequency alternate current is inputted into the voice coil 3 through a lead wire, the alternate current flows at a lower end of the voice coil 3 which is inserted into the case 1, to form a magnetic field while interacting with the magnet 2.
At this time, when the magnetic field is formed in the same direction as a magnetic filed formed by the magnet 2, attractive force is generated between the magnet 2 and the voice coil 3 to lower the voice coil 3. If a polarity of a current which flows through the voice coil 3 is converted into a reverse polarity, repulsive force is generated between the magnet 2 and the voice coil 3 to raise the voice coil 3.
By repeatedly lowering and raising the voice coil 3 using the high frequency current inputted into the voice coil 3, the vibrating plate 4 to which the voice coil 3 is attached moves up and down. By this upward and downward movement of the vibrating plate 4, a sound wave is generated.
In a speaker manufactured using a principle that the vibrating plate 4 is moved up and down by the inputted high frequency current to generate a sound wave, a high frequency signal such as a melody, a bell or a sound signal of a sender, which is inputted in advance into the voice coil 3, is discharged by the upward and downward movement of the vibrating plate 4 to perform the sounding function.
However, because the speaker can simply produce a sound, to afford not only the sounding function but also the vibrating function, a separate vibrating motor must be provided.
On the other hand, as demands toward miniaturization and thinning of a communication device are increased, while it is necessary for several components to be omitted and a size of the communication device to be reduced, a speaker and a vibrating motor are still used together for notifying the reception of an incoming call in a communication device.
Recently, various vibration generating apparatuses for simultaneously performing a speaker function and a vibration function are disclosed in the art. A typical example of these vibration generating apparatuses is described in Japanese Patent Laid-Open Publication No. Heisei 10-14195 (published on Jan. 16, 1998) as shown in FIG. 2.
The vibration generating apparatus includes largely a permanent magnet 300 fastened to a fastening member 400, upper and lower yokes 310 and 320 attached to upper and lower surfaces of the permanent magnet 300 for preventing magnetic flux from being leaked and forming a magnetic flux path, a coil 121 arranged such that it is crossed with the magnetic flux of the permanent magnet 300, a first vibrating body 120 supported to the fastening member 400 by a first elastic member 110, a second vibrating body 220 supported to the first vibrating body 120 by a second elastic member 210, and a current supplying section 500 connected to the coil 121 for supplying a current of a predetermined frequency to the coil 121.
In the vibration generating apparatus constructed as mentioned above, if a current is inputted into the coil 121 from the current supplying section 500, electromagnetic force is generated due to interaction between the permanent magnet 300 and the coil 121. Accordingly, by periodically changing the current flowing through the coil 121 to have a high frequency and a low frequency, electromagnetic force is periodically generated as external force to a magnetic circuit section having the permanent magnet 300 and the upper and lower yokes 310 and 320 and to the first vibrating body 120, and by this, a forced vibration occurs in a first vibration system 100 including the first vibrating body 120.
By this vibration, a second vibration system 200 is also vibrated, and as a result, vibrations are occurred in the first and second vibration systems 100 and 200 by the permanent magnet 300 and the coil 121.
That is to say, if a current having a frequency which corresponds to a natural vibration frequency of the first vibrating body 120 is inputted into the coil 121, vibrating function which is similar to conventional vibrating function is accomplished by the first vibrating body 120. Also, if a current having a frequency which corresponds to a natural vibration frequency of the second vibrating body 220 is inputted into the coil 121, a sound is generated by the second vibrating body 220.
However, in the vibration generating apparatus of the related art, since the vibrating function is performed by the fact that the first vibrating body 120 is vibrated to be collided with the case 400 to generate a vibration which is to be sensed by a user through the case 400, although a shock-absorbing material is attached to the case 400 at a place where the first vibrating body 120 is collided with the case 400, noise is generated by the collision, and since the vibration is transmitted through the first and second elastic members 110 and 210 to the case 400, lower vibration level is obtained.
Also, durability of the vibration generating apparatus is deteriorated due to the repeated collision between a bobbin 122 of the first vibrating body 120 and the case 400. Moreover, it is difficult to properly design material and shape for the first elastic member 110, the second vibrating body 220 and the second elastic member 210 and to determine elastic modulus for the first and second elastic members 110 and 210, whereby the vibration generating apparatus cannot be easily manufactured.